package algorithm.problems.dynamic_programming;

/**
 * Created by gouthamvidyapradhan on 17/03/2017.
 * Say you have an array for which the ith element is the price of a given stock on day i.
 * <p>
 * If you were only permitted to complete at most one transaction (ie, buy one and sell one share of the stock), design an algorithm to find the maximum profit.
 * <p>
 * Example 1:
 * Input: [7, 1, 5, 3, 6, 4]
 * Output: 5
 * <p>
 * max. difference = 6-1 = 5 (not 7-1 = 6, as selling price needs to be larger than buying price)
 * Example 2:
 * Input: [7, 6, 4, 3, 1]
 * Output: 0
 * <p>
 * In this case, no transaction is done, i.e. max profit = 0.
 */
public class BestTimeToBuyAndSellStocks {
    /**
     * Main method
     *
     * @param args
     * @throws Exception
     */
    public static void main(String[] args) throws Exception {
        int[] prices = {1, 1, 1, 1, 1};
        System.out.println(new BestTimeToBuyAndSellStocks().maxProfit(prices));
    }

    public int maxProfit(int[] prices) {
        if (prices.length == 0) return 0;
        int[] max = new int[prices.length];
        max[prices.length - 1] = prices[prices.length - 1];
        for (int i = prices.length - 2; i >= 0; i--) {
            max[i] = Math.max(prices[i], max[i + 1]);
        }
        int result = Integer.MIN_VALUE;
        for (int i = 0, l = max.length; i < l; i++) {
            result = Math.max(result, max[i] - prices[i]);
        }
        return result;
    }
}
